The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent that it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A catalytic converter, for example, a three-way catalytic converter (TWC), may be used with an internal combustion engine to reduce emissions. “Three-way” refers to the three emissions that a catalytic converter reduces, including carbon monoxide (CO), unburned hydrocarbons (HCs) and nitrogen oxide (NOx). For engines that are selectively operated in a lean mode, a lean NOx trap (LNT) may be provided downstream from the TWC. The LNT supplements the TWC to reduce NOx emissions when the TWC becomes less efficient under lean exhaust condition.
Fuel injected into the engines may contain sulfur. Sulfur is not combusted in the engines and is carried by exhaust gases through the TWC to the LNT. Sulfur may accumulate in the LNT. Sulfur accumulation adversely affects the trapping efficiency of the LNT.